Originally, metal filing cabinet case envelopes or shells were made from separate side, top, back and bottom walls welded or otherwise fastened together and then painted on the outside. Drawers were made in much the same manner with the separate bottom, sides and end walls welded or otherwise fastened together.
While many filing cabinets are still constructed this way today, alternate methods of assembly have arisen which have allowed manufacturers to construct file cabinets from pre-painted or prefinished steel. Because the finish on pre-painted steel is ruined if welded, requiring the metal to be repainted, it is highly desirable to avoid welding as the method for assembling the component pieces into a final filing cabinet. One proposed alternative cabinet design employs extruded corner posts with long narrow slots which slidably engage separate, pre-painted, rectangular shaped side and end pieces, thereby avoiding welding or even riveting the pieces together. Other proposed designs for cabinets or similar structures rely upon folding various portions of a single piece of pre-painted metal together and either interlock the portions or use mechanical fasteners. Such designs, however, would not achieve the low cost, light weight, simplicity and high strength provided by the present invention.
Appliance housings have been formed from prefinished or pre-painted metal by appliance manufacturers for some time. For example, refrigerators have been formed in this manner. However, refrigerator housings are typically made of heavy gauge steel and normally have an inner or second shell. This construction provides ample strength to the exterior housing structure.
Adhesively bonding or gluing cabinet case envelopes together is used for cardboard or wood boxes. However, cardboard boxes have neither the structural strength nor the exterior appearance found in a metal cabinet. In the case of wood boxes, strength is certainly available but limitations as to exterior appearance and weight become significant factors. Adhesively bonding cabinets of any material raises a manufacturing problem of holding or restraining the cabinet while the adhesive sets. This adds both time and expense to the manufacture of the product by requiring special clamps or vises as well as the labor necessary to install and remove these clamps or vises.
The prior art discloses that a rectangular shelf, divider, or other generally horizontal web can be mounted in a sheet metal cabinet by folding two or more of its four edges down into flanges, butting the faces of the flanges against the side and back panels of the cabinet and joining the flanges and panels.
Cabinets having a vertical stack of drawers, at least two of which are partitioned by a horizontal web within the cabinet, are also known. The partition prevents one from obtaining access to a drawer by removing other drawers from the cabinet, as when some drawers are for storing documents in general use and other drawers are for securing more valuable or sensitive documents.
Sectional cabinets, each encasing one drawer, are also known. Several of these can be stacked to form a complete multi-drawer filing cabinet. Provisions can be made to join a stack of sectional cabinets, preventing them from coming apart while in use.
The use of one or more straps spanning the width of a file cabinet (generally between two drawers of a vertical stack) and directly or indirectly joined to each side wall is known. The straps strengthen the cabinet, preventing its sides from bowing out when the drawers are heavily weighted or the cabinet is otherwise stressed during shipping or use. The straps have particularly been employed near the front of the cabinet, as the back panel of the cabinet typically prevents the side panels from bowing at the rear of the cabinet.